Tyranny of the old?

Just as we have a minimum age to be eligible to vote, should we have a maximum age for voters? If the idea is that a seventeen year old can't quite understand the world and make rational choices, then couldn't we make the same argument about, say, an 89-year old?
Similarly, when we have minimum age requirements to be an elected official, how come we do not have maximum age limitations? I remember Strom Thurmond never making any sense.

So, while in a prior blog entry I referred to the discussion on whether death can become optional, I am equally concerned about politics, and the benefits of political decisions, being dominated by the elderly, leaving the dwindling younger generations to pay the price.